An analysis of birthweight and gestational age in relation to concomitant variables such as placental weight, body length, socioeconomic index, head circumference as well as their relationship to antecedent-maternal variables and to subsequent outcome, such as neurological disorders in surviving children is being conducted on the Collaborative Perinatal Project offspring population. It is intended that Empirical Risk Tables and Birthweight Index will be generated which will be of some predictive value in relating antecedent factors to birthweight-gestational age outcomes. Plans are underway to incorporate the entire body of information generated in the form of a monograph which would be of use to clinicians.